Traditionally, the polyester repair markets have utilized well-defined processes in the area of damage repair. Unsaturated polyester resins, primers, fillers, adhesives, or putties are used to resurface and reshape damaged areas. For ease of understanding, the term “resin” will be used in the following description; however, it is to be understood that the term includes cured resins and prepolymers (uncured resins), primers, fillers, adhesives, and putties. The method for catalyzation and application of the resin is as much an art as it is a science. This is due in part to the very small amount of peroxide hardener (catalyst) that is used to cure the much larger amounts of unsaturated polyester resin properly. The optimum peroxide level needed to cure the resin is generally about 1 to 3 parts per hundred of the resin by weight. The resin and peroxide are packaged in separate containers, typically a large can for the filler (8 oz. to 55 gal.), and a small tube for the peroxide catalyst (0.25 oz. to 4 oz.).
The user dispenses a variable amount of resin into a cup or onto a mixing board, and adds the peroxide catalyst, essentially guessing at the correct amount for proper catalyzation. The consequences of improper catalyzation of the resin include loss of adhesion to the substrate, uncured surface (tacky), cracking of the resin due to excessive heat generation, migration of uncured resin organics to subsequent coatings resulting in discoloration of top coats, outgassing of uncured material in the presence of ultraviolet or heat energy from sunlight or paint baking systems resulting in blistering and other damage to the topcoat, as well as other problems that may require removal and replacement of the repair.
It has been difficult to create of a peroxide catalyst with a more reasonable mix ratio to the unsaturated polyester resins. The standard benzoyl and ketone peroxides use plasticizers such as phthalates as carriers. Phthalates are non-reactive and represent up to about 50% of the peroxide catalysts in commercial se. The non-reactive nature of the carrier does not adversely affect performance of the cure at levels of 1.5 to 3 parts per hundred unsaturated resin, but levels above 5 parts per hundred can disrupt the cure.
There remains a need in the art for a polyester resin composition that provides a more equal mix ratio between the resin and catalyst components.